It is proposed to study the role of cyclic AMP and cyclic GMP in nervous tissue. One approach is to purify and characterize the substrate for cyclic GMP-dependent protein kinase in nervous tissue. A second approach is to characterize the calcium-dependent phosphorylation system in membranes prepared from synaptosomes. A third approach is to study the localization of the synaptic membrane protein, using immunocytochemical as well as subcellular fraction techniques, that acts as a substrate for cyclic AMP-dependent protein kinase.